Method and means for comparing and selecting radiosignals



R. H. RANGER "Deg- 24, 1929.

METHOD AND MEANS FOR COMPARING AND SELECTING RADIOSIGNALS Filed Feb. 1a,1923 2 Sheets-Sheet 33mm muZuuum IlllllllHl lllll mmul-m Hlhl,

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METHOD AND MEANS "FOR COMPARING AND SELECTING RADIOSIGNALS File 16; 1923v 2 Sheets-Shet 2 K I. 2 D F.

u; 23 g I l 3 u: I LI 2 E ii (x RELAY UR RECORDER RH. RANGER PatentedDec. 24, 1929 @FFW RICHARD HOWLAND RANGER, OF BROOKLYN, EIEVT YORK,ASSIGNOR TO RADIO COR- PORA'IION OE AMERIGA, A CORPORATION OF DELA'WAREMETHOD AND MEANS FOR COMPARING AND SELECTING- RADIOSIGNALS Applicationfiled February 16, 1923. Serial No. 619,358.

This invention relates to means for improving the reception of radiosignals, particularly at times when the reception is likely to beinterrupted by local disturbances, such as at mospherics or staticdisturbances.

It has been found that atmospheric disturbances in general are local incharacter and if receiving stations are located at widely separatedpoints, they are only rarely interrupted by static disturbancesoccurring at each station at substantially the same time. I have takenadvantage of this to devise a system of receiving radio signals at aplurality of receiving stations which may be and preferably are widelyseparated from each other. In this system which is described and claimedin my copending application Serial No. 514,456 filed October 27, 1921for methods and means of receiving signals I have provided anarrangement in which records of the signals from a plurality of stationsare placed on a single sheet, preferably in juxtaposition. The operatorin reading the signals will read the record from any one of thestations, at the same time comparing the record which he is reading withthe record from the other stations recorded alongside. In case there isa discrepancy between the several records, the operator can generallydetermine by the indications of the separate stations what thetransmitted signal actually was.

In the present invention I have provided a method and means forelectrically comparing the signals received at a plurality of stationsand indicating by means of a single indicator as a signal the result ofsignals received at a plurality of stations. It has been found that thisinvention provides a system which will permit of signals being receivedand an intelligible record thereof being ob tained by utilizing aplurality of receiving stations, under conditions which would'malre theseparate signals received at any one of the stations in the system verydiiiicult, if not im possible, to read and this is done by providingthat the signals from each station ultimately actuate a singleindicating system which is provided with controlling means which are soarranged that the cooperation of all stations is required in such amanner that in general if the correct signal is obtained at any stationthe correct signal is selected and indicated. This may be done byproviding relays at each receiving station which cause the operation ofthe common indicator at the signal recording station in such a mannerthat the indicator responds when any of the station relays haveresponded. However, I have found that benefits of this system may bestbe utilized by providing for reverse Morse signalling; or by reversingthe relay contacts; that is to say, the relays at each station energizethe line to the recording station during the spacing periods, instead ofduring the actual signalling periods. In connection with this reversedsignalling I prefer to use a limiting cut-off in the receiving stationsuch as described and claimed in my 00- pending application Serial No.619,359, filed February 16, 1923.

My invention is shown in the accompanying drawing in which Fig. 1 showsthe preferred form of my system,

Fig. 2 is a chart showing the cooperation of the various receivingstations in producing the resultant indication at the recording station,and

Fig. 3 is a view of one form of apparatus constituting the limitingcut-off according to the above entitled application, and

Fig. l is a modification of my relay arrangement.

My invention will best be understood both as to its underlying theoryand its practical construction and operation by reference to thespecification and the attached drawing but its scope will beparticularly pointed out in the appended claims.

Referring to 3 showing one form of limiting cut-oil which may beutilized in this system, there is provided a receiving antenna 1grounded in the usual manner and provided with a heterodyne supplyingsuch a frequency as will give a 8,000 cycle beat with the receivedsignal. Coupled to this antenna by means of'coil 3, I provide a resonantcircuit the output of which is led to a radio frequency amplifier; theoutput from this amplifier is fed to a rectifier from which therectified currents of super-audible frequency are again amplified andfed into a balanced rectifier which in itself is a device for reducingthe efie-cts of static. This arrangement which is more particularlydescribed in my copending application Serial No. 581,350, filed August12, 1922, comprises two three-electrode tubes having the grids connectedto opposite ends of the secondary of transformer 18 through gridcondensers 19 and 20 shunted by grid leaks 21, 22. The middle point ofthe seconeary is connected to the cathode of the tubes and the platesare connected together and to the filament through the plate battery 23and the coil 24. This arrangement serves substantially to balance theinitial impulses, but received currents cumulatively decrease the outputof both tubes, so that the large initial impulses of highly dampedstatic are substantially balanced, as well as the small initial impulsesof signals. The sustained impulses gradually increase the negativecharge 'on each of the grids so that the resultant plate currentdecreases when a sustained alternating current is impressed on thegrids, but a 6,000 cycle variation occurs in the plate current. Thissuper-audible pulsation of 6,000 is impressed on a galvanometer 25 by means of a coupling coil 26 and in addition it is desirable to impress anaudible frequency of 1,000 on the system preferably by means of a lightplaced to shine on the galvanometer mirror, which light is interruptedby any suitable means, such as a rotating shutter 27 at the desiredfrequency. The mirror of the galvanometer receives and reflects light ona photoelectric cell 28 when the deflection of the mir ror is such thatthe light is reflected on the aperture of the cell. In this modificationthe galvanometer and the photo electric cell constitute thenon-integrating limiting cut-off relay. The recording galvanometer ofthis type is particularly described in various patent applications of C.A. HoXey, of which Serial No. 420 191, filed October 29, 1920, willserve as illustration. The current from the photo electric cell is ledthrough a circuit tuned to 1,000 cycle variation, rectified andimpressed on a suitable relay.

It will be apparent that when a transmitted wave is received the lightwill be deflected off the photo electric cell and the relays and allfollowing circuits will thereupon be opened. I utilize this limitingcutoff in my system. as shown in Fig. 1, where I provide for examplethree receiving stations C, D and E each of which may be constructed asabove described. The output current from each relay is respectively ledto coils 10, 11 and 12 for controlling a plurality of relay contacts forthe coil of relay 14. It will be apparent that whenever the circuits ofcoils of relays 10, 11 and 12 are open as when a signal is beingreceived at all stations, the relay armatures will be pulled away fromthe contacts by the springs attached thereto and as a result the circuitfrom battery 13 through the coil of relay 1% will be opened thusallowing the spring attached to the armature of this relay to close itthereby closing a local circuit through indicator 15, which may be arecorder if desired.

Referring to Fig. 2 A shows the signals as transmitted. B shows theinverted signalling current which would be fed to coils 10, 11 and 12 ifthe operation of each station were not interfered with by static. C, Dand E and C, D and E show rectified currents received at each stationand the inverted currents of the three stations which are obtained byutilizing the limiting cut-off relay.

Each of these is mutilated at certain portions by heavy static so thatnone of the signals reads properly, the condition being aggravated forpurpose of illustration. Station G has static so that the receivedsignal might be read as dash, dash, space, dash; station D as dot, dash,dash; station E as dash, dash, space, dot. The limiting cut-ofi deviceof each receiver, however, does not pass current through the relays 7,8, and 9 during the periods when signal currents are received and themutilation in the inverted currents p ssing through the relays occursonly duri the intermediate spacings. At the beginning of the signalrelays 10, 11, and 12 are each supplied with current from relays 7, 8, 9and as all three parallel relays are closed the battery circuit 13 isclosed which causes the relay 1%: to open the circuit of the indicator15. During the space preceding the first dot, the relay 12 is openedwhen the static e is received by station E. Relay 10 is also opened dueto the static 0, of station C, but the battery circuit remains closed byrelay 11 as no static currents are received by station 8 during theperiod preceeding the first dot and the local indicator circuittherefore remains open and the preliminary space is recorded properly.During the first dot all of the relays are open due to the fact that thelimiting cut-off relay operated by the signal current has deenergizedthe coils of relays 10, 11 and 12. At the end of the first dot therelays 11 and 12 will be closed as no signal is received at stations Dor E and the indicator circuit will be opened at the end of the dot, inspite of the fact that'the relay 10 has been opened due tostatic'cur'rent c of station C.

Similarly the dash and the space will be correctly indicated by theindicator in spite of static (Z and (l of station D and the dot will becorrectly indicated in spite of static c (Z of stations C and D, becausethe indicator will only operate when all the relays 10, 11 and 12 areopen simultaneously. If any portion of the message is received withoutinterference at any one of the stations the resulting indication will becorrect.

It will be apparent, however, that it desired I may provide the relaycontacts 10, 11 and 12 in series directly in the local indicator circuitas shown in Fig. 4. The elec trical selection of signals by thisarrangement is the same as described above.

While I have shown and described this arrangement in particular for asystem utiliza reversal either of the signal or of the relay contacts atthe receiving stations, that is for inverted signal current in relays10, 11 and 12, it will be apparent that it is within the scope of myinvention to utilize simply an ordinary relay at each receiving stationwithout the limiting cut-ofi and provide at the recording station aseries of relays connected in such manner that only the signals whichare received simultaneously at all the receiving stations will actuatethe local inclicator.

Furthermore, while I have shown here the utilization of the principlesof this invention by means of electro-magnetic relays, it will beobvious that I may use other types of relays such, for example, asthermionic tubes, as more particularly set forth and claimedspecifically in my copending application Serial No. 609,37 6 filedDecember 28, 1922, for rectifier polarizer.

It is obvious that this invention is not limited to the precisearrangements shown and described, but modifications and changes may bemade without departing from the scope of my invention, as pointed out inthe appended claims.

Having described my invention, what I claim is:

1. In a radio receiving system, a plurality of geographically spacedantenna systems for receiving the same signals, means associated witheach of said antenna systems for receiving and detecting the signalspicked up by said antennas, a wire line associated with each of saidreceiving systems and leading therefrom to a common point, relaysassociated with each of said receiving systems for energizing therespective wire lines during the spacing periods in received signals, anindicator at the said common point arranged to produce indications onlyat periods when all of said transmission lines are deenergized.

2. In a radio receiving system, a plurality of geographically spacedantenna systems each arranged to receive the same radio sig nals, areceiving system associated with each of said antenna systems fordetecting and receiving the signals picked up thereby, a line connectingeach of said receiving systems to a common point, a relay systemassociated with each of said lines and arranged to energize the lineonly at periods when there is an absence of signals at the receivingstation, an indicator, and means for causing the actuation of saidindicator only at periods when all of said lines are deenergized.

3. In a radio receiving system for the reception of signals throughatmospheric disturbances, the combination of a plurality of receivingsystems so situated as to be exposed to substantially different fieldsof atmospheric disturbances, each receiving system comprising a relayhaving a normally energized output circuit and means controlled byreceived signals for deenergizing said output circuit in response tosignals, an indicator and means cooperating with each of said normallyenergized relay circuits and with said indicator for actuating saidindicator only when all of said output circuits are deenergized.

4. In a radio signalling system for receiving signals throughatmospheric disturbances, the combination of a plurality of receivingsystems exposed to substantially different fields of disturbances, andeach comprising a relay having a normally energized output circuit andmeans for deenergizing said output circuit upon receipt of desiredsignals comprising a light sensitive cell, means coopcrating with saidcell for normally projecting light thereon when desired signals are notreceived and operative in response to desired signals to divert lighttherefrom, whereby said relay circuit is deenergized, an indicator,means cooperating with each of said relay circuits and with saidindicator to ac tuate said indicator only when each of said relaycircuits is deenergized.

5. In a radio signalling system for receiving signals throughatmospheric disturbances, the combination of a plurality of receivingsystems exposed to substantially different fields of atmosphericdisturbance, and each comprising a relay normally having its outputcircuit energized when desired signals are not received and means forcausing deenergization of said relay circuit on receipt of desiredsignals, comprising a light sensitive cell, means for normallyprojecting light thereon when desired si nals are not receivedcomprising a galvanometer and means for deflecting light therefrom whendesired signals are received comprising means for energizing saidgalvanometer when desired signals are received, an indicator, and meanscooperating with said indicator and with each of said relay circuits toenergize said indicator only when all of said relay circuits aredeenergized.

6. In a radio signalling system for receiving signals throughatmospheric disturbances, the combination of a plurality of re ceivingsystems so situated as to be exposed to atmospheric disturbances ofsubstantially different character, and each of said systems comprising arelay having an output circuit normally energized when desired signalsare not received, and means for deenergizing said relay circuit inresponse to receipt of desired signals, comprising a photo electriccell,

means for normally projecting light thereupon When desired signals arenot received, comprising a galvanometer, means for energizing saidgalvanometer to deflect light away therefrom comprising a circuitnormally hav ing a predetermined current flow therein, and means fordecreasing current flow iherethrough in response to desired signals, anindicator, and means cooperating with each of said relay circuits andWith said indicator for causing energization thereof only when all ofsaid relay circuits are deenergized.

RICHARD HOVLAND RANGER.

